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Model Context Protocol (MCP) connects models to tools and context. Use it to give ZeroTwo or ZeroCode access to third-party documentation, or to let it interact with developer tools like your browser or Figma. ZeroTwo web can use remote MCP-backed tools supplied by plugins. Local ZeroCode clients can also connect directly to MCP servers and share their configuration.
The ZeroTwo desktop app, and desktop app support MCP servers and share MCP configuration for the same ZeroCode host.The supported server features below apply to MCP servers configured on a ZeroCode host. Hosted plugin tools can have different capabilities.

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Supported MCP features

  • STDIO servers: Servers that run as a local process (started by a command).
    • Environment variables
  • Streamable HTTP servers: Servers that you access at an address.
    • Bearer token authentication
    • OAuth authentication
    • ZeroTwo session authentication for trusted first-party servers
  • Server instructions: ZeroCode reads the MCP instructions field returned during initialization and uses it as server-wide guidance alongside the server’s tools.
If you build or maintain an MCP server for ZeroCode, use instructions for cross-tool workflows, constraints, and rate limits that apply across the server. Keep the first 512 characters self-contained so the most important guidance is available when ZeroCode is deciding how to use the server.

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Connect ZeroCode to an MCP server

ZeroCode stores MCP configuration in config.toml alongside other ZeroCode configuration settings. By default this is ~/.zerotwo/config.toml, but you can also scope MCP servers to a project with .zerotwo/config.toml (trusted projects only).The ZeroTwo desktop app, and desktop app share this configuration. Once you configure your MCP servers, you can switch among those clients without redoing setup.

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STDIO servers

  • command (required): The command that starts the server.
  • args (optional): Arguments to pass to the server.
  • env (optional): Environment variables to set for the server.
  • env_vars (optional): Environment variables to allow and forward.
  • cwd (optional): Working directory to start the server from.
  • experimental_environment (optional): Set to remote to start the stdio server through a remote executor environment when one is available.
env_vars can contain plain variable names or objects with a source:
String entries and source = "local" read from ZeroCode’s local environment. source = "remote" reads from the remote executor environment and requires remote MCP stdio.

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Streamable HTTP servers

  • url (required): The server address.
  • auth (optional): Authentication to try after configured bearer tokens and authorization headers. Use oauth (the default) for stored MCP OAuth credentials. Use chatgpt to use the current ZeroTwo session for the trusted first-party ZeroTwo origin, with stored OAuth as a fallback.
  • bearer_token_env_var (optional): Environment variable name for a bearer token to send in Authorization.
  • http_headers (optional): Map of header names to static values.
  • env_http_headers (optional): Map of header names to environment variable names (values pulled from the environment).
If no credential source resolves, ZeroCode can connect to the server without authentication. Run zerocode mcp login <server-name> separately to start an MCP OAuth login.

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Other configuration options

  • startup_timeout_sec (optional): Timeout (seconds) for the server to start. Default: 10.
  • tool_timeout_sec (optional): Timeout (seconds) for the server to run a tool. Default: 60.
  • enabled (optional): Set false to disable a server without deleting it.
  • required (optional): Set true to make startup fail if this enabled server can’t initialize.
  • enabled_tools (optional): Tool allow list.
  • disabled_tools (optional): Tool deny list (applied after enabled_tools).
  • default_tools_approval_mode (optional): Default approval behavior for tools from this server. Supported values are auto, prompt, writes, and approve. The writes mode prompts for tools that aren’t marked read-only.
  • tools.<tool>.approval_mode (optional): Per-tool approval behavior override.
If your OAuth provider requires a fixed callback port, set the top-level mcp_oauth_callback_port in config.toml. If unset, ZeroCode binds to an ephemeral port. If your MCP OAuth flow must use a specific callback URL (for example, a remote Devbox ingress URL or a custom callback path), set mcp_oauth_callback_url. ZeroCode uses this value as the base callback URL, then appends a server-specific callback ID to produce the OAuth redirect_uri it sends during login. Register the full derived redirect_uri with your OAuth provider, including the appended callback ID and any configured path, query, or port, rather than registering only the base host or path without that suffix. Local callback URLs (for example localhost) bind on the local interface; non-local callback URLs bind on 0.0.0.0 so the callback can reach the host. If the MCP server advertises scopes_supported, ZeroCode prefers those server-advertised scopes during OAuth login. Otherwise, ZeroCode falls back to the scopes configured in config.toml.

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config.toml examples

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Plugin-provided MCP servers

Installed plugins can bundle MCP servers in their plugin manifest. Those servers are launched from the plugin, so user config doesn’t set their transport command. User config can still control on/off state and tool policy under plugins.<plugin>.mcp_servers.<server>.

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Examples of useful MCP servers

The list of MCP servers keeps growing. Here are a few common ones:
  • ZeroTwo Docs MCP: Search and read ZeroTwo developer docs.
  • Context7: Connect to up-to-date developer documentation.
  • Figma Local and Remote: Access your Figma designs.
  • Playwright: Control and inspect a browser using Playwright.
  • Chrome Developer Tools: Control and inspect Chrome.
  • Sentry: Access Sentry logs.
  • GitHub: Manage GitHub beyond what git supports (for example, pull requests and issues).